Use spaces instead of tabs

[sosukesuzuki]

When we update tesst262 for WebKit, WebKit style checker warns for tabs (context: WebKit/WebKit#30940 ).

For consistency, I think we should use spaces instead of tabs.

[ljharb]

while tabs are far superior and more accessible, clearly we overwhelmingly use spaces, and we should be consistent

[sosukesuzuki]

Yes I agree with you, I personally don't care which one we use, but we need to be consistent.

[Ms2ger]

Certainly we shouldn't be inconsistent even within a single file